1. Field of the Invention
The present invention relates to a passive vehicle occupant restraint, such as an air bag, for restraining a vehicle occupant in the event of an impact on a vehicle, and more specifically to a technique for controlling activation of such a passive vehicle occupant restraint.
2. Description of the Prior Art
An apparatus for controlling squib ignition in an air bag is one of known activation control apparatuses for controlling activation of passive vehicle occupant restraints. In the air bag, a squib ignites a gas-generating agent in an inflator on impact, and a gas accordingly evolves from the inflator to inflate a bag and protect a vehicle occupant from the impact of a collision.
The apparatus for controlling squib ignition in an air bag typically measures the impact on the vehicle as a deceleration by an acceleration sensor, calculates a function of the measured deceleration, compares the calculated value of the function with a preset threshold value, and controls the squib ignition based on the result of comparison. The acceleration sensor is disposed at a predetermined position in the vehicle, generally on a floor tunnel in the vehicle. In the description hereinafter, the acceleration sensor mounted on the floor tunnel is referred to as the floor sensor.
The threshold value is set to be greater than the maximum among the values of the function calculated from the decelerations measured by the floor sensor when impacts applied to the vehicle have such a degree that does not require activation of the air bag.
In the conventional activation control apparatus for a passive vehicle occupant restraint, the impact applied to the vehicle is detected only by means of the floor sensor, and activation of the passive vehicle occupant restraint is controlled based on the result of detection. The following problems arise in this conventional structure.
Collisions of the vehicle are classified into several types by the condition and the direction of the collision and the type of the object against which the vehicle collides; that is, a head-on collision, an oblique collision, a pole collision, an offset collision, and an under-ride collision as shown in FIG. 27. In the case of a head-on collision, the vehicle receives an impact of the collision by left and right side members thereof, so that an extremely large deceleration arises on the floor tunnel with the floor sensor mounted thereon within a predetermined time period after the collision. In the case of collisions other than the head-on collision, however, the vehicle does not receive the impact of the collision in such a manner, so that no such a large deceleration arises on the floor tunnel within the predetermined time period after the collision.
Namely the floor sensor has higher sensitivity of detection of the impact within a predetermined time period after the collision in the case of a head-on collision, than in the case of the other collisions.
The threshold value is thus set mainly based on the deceleration measured in the case of a head-on collision. More concretely the threshold value is set based on the function calculated from the deceleration measured by the floor sensor when a head-on collision applies an impact of such a degree that does not require activation of the air bag to the vehicle.
This method for setting the threshold value based on the deceleration measured in the case of a head-on collision gives a relatively large threshold value. In the case of collisions other than the head-on collision, the floor sensor has relatively low sensitivity of detection of the impact within a predetermined time period after the collision as mentioned above. A DSP (digital signal processor) is accordingly used for Fourier transform of the deceleration signal obtained in the event of the collision to characteristics of a specific frequency component. In the case of the other collisions (including an offset collision), the impact is detected based on the characteristics of the specific frequency component. This technique requires the DSP and the other related devices as well as a high-performance computer, which undesirably increases the cost.
The object of the present invention is thus to provide an activation control apparatus of simple structure that enables a passive vehicle occupant restraint to be activated with high accuracy, irrespective of the type of a collision.
At least part of the above and the other related objects of the present invention is realized by a first activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The first activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; impact detection means disposed at a position ahead of the impact measurement means in the vehicle for determining whether or not the impact applied to the vehicle is not less than a specified reference value; and threshold variation pattern changing means for, when the impact detection means determines that the impact applied to the vehicle is not less than the specified reference value, changing the specified threshold variation pattern to another threshold variation pattern.
The present invention is also directed to a first method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The first method includes the steps of:
(a) measuring a value of impact at a first position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a threshold value that varies according to a specified threshold variation, pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) determining whether or not a value of impact detected at a second position, which is ahead of the first position in the vehicle, is not less than a specified reference value when the impact is applied to the vehicle; and
(d) when the value of impact detected at the second position is determined to be not less than the specified reference value in the step (c), changing the threshold variation pattern to another threshold variation pattern.
In the present invention, the passive vehicle occupant restraint includes air bags, seat belt pre-tensioners, inflatable curtains as well as devices for stopping a fuel supply to an engine in the event of a collision and devices for releasing door locks in the event of a collision. The measurement of the impact and the value calculated from the measurement include an acceleration or a deceleration, a velocity, a moving distance (obtained by integrating the deceleration twice with respect to time), a moving average (obtained by integrating the deceleration over a fixed time period), the intensity of the deceleration at a specific frequency, and a vector component representing the deceleration in the direction of the length or the width of the vehicle. These definitions are applicable to the other apparatuses and methods discussed below.
The first activation control apparatus and the first method of the present invention change the predetermined threshold variation pattern to another threshold variation pattern in case that the value of impact detected at the second position in the vehicle is not less than the predetermined reference value, even when the type of the collision causes the value of impact to be not readily detected at the first position. By way of example, it is assumed that the predetermined threshold variation pattern is changed to another threshold variation pattern that gives a lower threshold value. In this case, when the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the passive vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the first position.
At least part of the objects of the present invention is also realized by a second activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The second activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; impact detection means disposed at a position ahead of the impact measurement means in the vehicle for determining whether or not the impact applied to the vehicle is not less than a specified reference value; and threshold value changing means for, when the impact detection means determines that the impact applied to the vehicle is not less than the specified reference value, changing the specified threshold value to another threshold value.
The present invention is further directed to a second method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The second method includes the steps of:
(a) measuring a value of impact at a first position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) determining whether or not a value of impact detected at a second position, which is ahead of the first position in the vehicle, is not less than a specified reference value when the impact is applied to the vehicle; and
(d) when the value of impact detected at the second position is determined to be not less than the specified reference value in the step (c), changing the threshold value to another threshold value.
The second activation control apparatus and the second method of the present invention change the predetermined threshold value to another threshold value, for example, to a lower threshold value, in case that the value of impact detected at the second position in the vehicle is not less than the predetermined reference value, even when the type of the collision causes the value of impact to be not readily detected at the first position. When the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the passive vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the first position.
At least part of the objects of the present invention is realized by a third activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The third activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; impact direction detection means for specifying a direction of the impact applied to the vehicle; and threshold variation pattern changing means for, when the direction of the impact specified by the impact direction detection means coincides with-a preset direction, changing the specified threshold variation pattern to another threshold variation pattern.
The present invention is further directed to a third method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The third method includes the steps of:
(a) measuring a value of impact at a predetermined position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) specifying a direction of the impact applied to the vehicle; and
(d) when the direction of the impact specified in the step (c) coincides with a preset direction, changing the specified threshold variation pattern to another threshold variation pattern.
The preset direction here includes a direction having an angle of not less than a specified value with respect to the center line of the vehicle (that is, the center line along the length of the vehicle).
The third activation control apparatus and the third method of the present invention change the predetermined threshold variation pattern to another threshold variation pattern in case that the detected direction of the impact coincides with the preset direction, even when the type of the collision causes the value of impact to be not readily detected at the predetermined position. By way of example, it is assumed that the predetermined threshold variation pattern is changed to another threshold variation pattern that gives a lower threshold value. In this case, when the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the passive vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the predetermined position.
At least part of the objects of the present invention is also realized by a fourth activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The fourth activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; impact direction detection means for specifying a direction of the impact applied to the vehicle; and threshold value changing means for, when the direction of the impact specified by the impact direction detection means coincides with a preset direction, changing the specified threshold value to another threshold value.
The present invention is further directed to a fourth method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The fourth method includes the steps of:
(a) measuring a value of impact at a predetermined position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) specifying a direction of the impact applied to the vehicle; and
(d) when the direction of the impact specified in the step (c) coincides with a preset direction, changing the specified threshold value to another threshold value.
The fourth activation control apparatus and the fourth method of the present invention change the predetermined threshold value to another threshold value, for example, to a lower threshold value, in case that the detected direction of the impact coincides with the preset direction, even when the type of the collision causes the value of impact to be not readily detected at the predetermined position. When the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the passive vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the predetermined position.
At least part of the objects of the present invention is realized by a fifth activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The fifth activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; collision type specifying means for specifying a type of a collision in which the vehicle crashes; seating state detection means for detecting a seating state of a vehicle occupant in the vehicle; and threshold variation pattern changing means for, when the type of the collision specified by the collision type specifying means coincides with a specified type of a collision and when the seating state detected by the seating state detection means coincides with a specified seating state, changing the specified threshold variation pattern to another threshold variation pattern.
The present invention is further directed to a fifth method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The fifth method includes the steps of:
(a) measuring a value of impact at a predetermined position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) specifying a type of a collision in which the vehicle crashes;
(d) detecting a seating state of a vehicle occupant in the vehicle; and
(e) when the type of the collision specified in the step (c) coincides with a specified type of a collision and when the seating state detected in the step (d) coincides with a specified seating state, changing the specified threshold variation pattern to another threshold variation pattern.
In the fifth activation control apparatus and the fifth method of the present invention, the type of the collision may be specified by any method, for example, a method of measuring the direction of the collision and the intensity of the impact or a method based on data obtained by Fourier transform of the waveform of the deceleration upon impact. The seating state of the vehicle occupant includes the wearing state of the seat belt, the position of the seat along the length of the vehicle, and the angle of the seat.
The fifth activation control apparatus and the fifth method of the present invention change the predetermined threshold variation pattern to another threshold variation pattern in case that the collision of such a type is expected and that the vehicle occupant is in the predetermined seating state, even when the type of the collision causes the value of impact to be not readily detected at the predetermined position. By way of example, it is assumed that the predetermined threshold variation pattern is changed to another threshold case, when the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the passive vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the predetermined position.
At least part of the objects of the present invention is also realized by a sixth activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The sixth activation control apparatus includes: impact measurement means disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation control means for comparing a value calculated from the measurement of the impact by the impact measuring means with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; collision type specifying means for specifying a type of a collision in which the vehicle crashes; seating state detection means for detecting a seating state of a vehicle occupant in the vehicle; and threshold value changing means for, when the type of the collision specified by the collision type specifying means coincides with a specified type of a collision and when the seating state detected by the seating state detection means coincides with a specified seating state, changing the specified threshold value to another threshold value.
The present invention is further directed to a sixth method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The sixth method includes the steps of:
(a) measuring a value of impact at a predetermined position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a specified threshold value, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) specifying a type of a collision in which the vehicle crashes;
(d) detecting a seating state of a vehicle occupant in the vehicle; and
(e) when the type of the collision specified in the step (c) coincides with a specified type of a collision and when the seating state detected in the step (d) coincides with a specified seating state, changing the specified threshold value to another threshold value.
The sixth activation control apparatus and the sixth method of the present invention change the predetermined threshold value to another threshold value, for example, to a lower threshold value, in case that the collision of such a type is expected and that the vehicle occupant is in the predetermined seating state, even when the type of the collision causes the value of impact to be not readily detected at the predetermined position. When the collision applies an impact of such a degree that requires activation of the passive vehicle occupant restraint to the vehicle, the value calculated from the measurement of the impact may exceed the threshold value within a predetermined time period after the collision. Such a simple structure accordingly enables the pass vehicle occupant restraint to be activated with high accuracy, even when the type of the collision causes the value of the impact to be not readily detected at the predetermined position.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.